The present invention relates to an electronic component package structure that employs a semiconductor laser (LD) and a fabricating method therefor, and in particular, to a semiconductor laser device to be built in an optical pickup for use in an optical disc system of, for example, compact disc or digital video disc and a fabricating method therefor.
Conventionally, with regard to the semiconductor laser device, an hermetically sealed airtight type device, which employs a CAN type metallic stem, is going mainstream. Moreover, with regard to the semiconductor laser device, CAN type stems of the standard configurations of diameters of 5.6 mm and 9 mm are normally used for optical pickups intended for, for example, compact discs and digital video discs. FIGS. 4A and 4B show the basic structures of these stems.
A semicircular columnar chip mounting section 52 is formed on a disc-shaped stem 51 in a central position thereof, and openings 53 and 53 for receiving leads 55 and 56 therethrough are formed through the stem 51 in the vicinity of this chip mounting section 52. Then, the leads 55 and 56 are inserted through the respective openings 53 and 53, and the openings are peripherally filled with a low melting point glass 54 in order to secure insulation of the leads 55 and 56 from the stem 51, thereby fixing the leads 55 and 56 to the stem 51.
On the other hand, a semiconductor laser element 57 is mounted on a reference surface (mounting surface) 52a of the chip mounting section 52, and connected to one lead 56 via a wire 58.
Then, by mounting and fixing a cylindrical cap section 59 onto the stem 51 in this state, a semiconductor laser device of the CAN stem type shown in FIG. 4B is completed.
In order to improve the hermetic characteristic and transmittance at a specified wavelength, an AR-coated glass member 591 is stuck to a laser light-emitting window 59a of the cap section 59 with a low melting point glass or the like.
As a device that belongs to the CAN stem type semiconductor laser device, a semiconductor laser unit described in Japanese Patent Laid-Open Publication No. 2000-77792 can be enumerated.
Moreover, a semiconductor laser device of an inexpensive open package structure called the “frame laser ” in which a lead frame and resin are molded in an integrated body has recently appeared mainly for the compact disc playback use. FIG. 5 shows the basic structure of the semiconductor laser device of this open package structure.
A plurality of sets of three leads 61, 62 and 63 are joined to one another via a tie bar 60 to form a lead frame, and each of the sets of leads 61 through 63, thus joined to one another, is integrally molded with a resin material 64 that becomes a housing. Subsequently, a semiconductor laser element 65 is mounted on a chip mounting surface 62a formed at the tip of the lead 62 positioned at the center. By electrically connecting this semiconductor laser element 65 with one side lead 63 via a wire 66 and finally severing the tie bar 60, a semiconductor laser device of the open package structure is completed.
In the package of the hermetic structure of the CAN type that employs the conventional metallic stem, the metallic stem 51 and the metallic cover (cap section 59) called a cap are employed, which results in an increased number of components. Moreover, it is a general way to stick the AR-coated glass member 591 to the laser light-emitting window 59a of the cap section 59 with a low melting point glass or the like in order to increase the hermetic characteristic and transmittance at the specified wavelength, and this has disadvantageously been a bottleneck in reducing the cost of the components.
Moreover, it is required to secure the insulation of the leads 55 and 56 against the stem 51, and therefore, in implanting the leads 55 and 56 in the stem 51, the leads 55 and 56 are retained with interposition of the low melting point glass while maintaining the hermetic characteristic. This has led to the problem that the stems 51 have been obliged to be supplied separately, so that it is impossible to realize an efficient process of assembling the devices in a joined state.
On the other hand, in order to solve the aforementioned problems of the CAN type laser package, the laser package of the structure called the “frame package ”, in which the lead frame and the resin housing are molded in an integrated body, as described above, has been developed.
However, there has been an immanent problem that a heat dissipation characteristic, which has not become a serious problem since the semiconductor laser element is mounted on the metallic stem portion in the CAN type package, is deteriorated in the “frame laser ”, and this has led to the problem that a laser chip (semiconductor laser element) of a bad thermal characteristic and a high-output laser chip with large heat generation cannot be mounted. Moreover, on the background that the “frame laser” has been developed giving priority to its productivity and price, no industry-standard configuration has been determined, and this has led to the problem that the configuration of the pickup housing is obliged to be altered in order to make full use of the device on the user side.